Apparatus for hydrodynamictesting of ship models



June 19, 41945. l2,378,412 APPARATUS FOR HYDRoDYNAMIc-TESTINGAOF SHIPMODELS C. A. LEE

Filed Jan. 18, 1944 w .36. B w e ...mm 4 7/ vom Il mw E .I 7 7` 6 w 5 m 6l ho. M WT n -HH..|........ ma u. llll l.. W 6 l. sl. .1|.5 D 1 o y... l. i4.

Patented June 19, 1945 Y APPARATUS FOR HYDRODYNAMIC- TESTING OF SHIP MODELS harlesA. Lee, United States Navy,

- Laramie, Wyo.

Q Application January 18,1944, serian No. 518,779 iciaims. (o1. vs -14s)4 l nv(Grral'ltedjunder the act of March y3,'18'83, as amended April 30, 1928; '370 O. G. 757) l The invention relates to measuring and testing apparatus `and to an? improved fluid flow meter.- i

ln the hydrodynamic testingof models of ships,

boatsk and various nautical devices, the models are towed or guided along a predetermined course through 4normally Stillwater in an elongate testing basin. :Movement of the 4towed modelthrough the normallystill water tends to'create a current therein which, however slight, may affect the accuracy of thefresults'. A-An important-object of the present' invention-is to provide, for use with a still-water testingbasin equipped with a car` riage'fortowing'or guiding models alongra predetermined course, apparatus vfor measuring any ow of Water in thebasin inthe direction of said course ahd'in a zonein theyicinity ofathegmodel being towed.` f Another object of the inventionis to provide a meter. which, willindicate small dilferences between the actual ratefof movement of a fluidrelf vative to a body, and a reference rate' normally `closely,approximatingthe actual rate. A furtherobject is the provision of; a fluid flow meter for attachment to a land vehicle and which will positively indicate any slightmovement, with respect'tothe ground and in the direction of travel of the vehicle, or uid inthe vicinity of thevehicle.

` Y 'Y Other objects and advantages' 'ofthe invention will become apparent during thecourseof the followingvdetailed description, taken inconnection with' the accompanying drawing, forming a part of this specification, and in which drawing, Figure 1 is a view, partly in vertical transverse section and partly in front elevation, of a stillwater testing basin provided with` a model towing carriage lequipped with my uid flow meter, ak small portion of the starboard'side of the carriage being broken away to illustrate the arrangement of parts. I ,y

Figure 2 is a View, partly in vertical'transverse section and partly in front elevation, of the right front wheel of the carriagev and its associated parts. Y v

Figure 3 is a View, partly in Vertical longitudinal section and partly in side elevation', of the uid operated propeller and its bracket.

Figures 4 and 5 are transverse sectional detail Views substantially onrthe lines 4--44 vand 5-5, respectively, in Figure 3.

` Figure 6k isa diagrammatic Viewv of a measuring circuit preferably forming a part of the apparatus. r

In the drawing, which for the purpose of illustration showsl only a preferred embodiment of the invention, and where `similar 'reference charactersdenote corresponding parts throughout the.. several Views, the letter A designates a still-Watertesting basin provided with a model The testing basin A preferably is a long, narrow, rectangular, openr structure containing water. Il)r and including longitudinal sidewalls II,

,I2 which horizontally support a pair of spaced parallel rails I3,` I4 forming a track. Transversely spanning the testing basin A and movable longitudinallythereof on the rails I3, I4, is the wheeled carriage, B which, in the example shown,

is made of Welded steel tubing I5 in the form of a bridge., Attached` to the starboard side of the "erator' shaft I 9.

Attached to the carriage B, preferably'at'the o middle thereof, as by suitable mechanism including a downwardlyextending bracket 26, is the model; 2l to be tested. Fixed to the carriage,

, preferably forwardly of the bracket26, as by bolts 28, is the downwardly extending uid ow meter assembly D, shown more specifically in Figure 3. .The carriage, in moving along the rails I3, I4

will tow the assembly D and the model 21, along a rectilinear course longitudinally of the testing basin A.

The uid flow meter assembly D includes a housing 3'0 having a submerged hydrofoil portion 3I so streamlined that it may be towed through the water -ID Without causing appreciable disturbance thereto. Supported for rotation in the submerged portion 3| about anV axis extendingin vthe direction of travelof the carriage, as by Ianti-friction bearings` 32, 33, is a shaft 34 having a forwardly projecting end portion 35. yFixed on the shaft 34, as by a set screw 36, is a cylindrical memberk 31, formed of an electrically insulative material, and encircledat vits reduced rear end with an electrically conclue-'- tive ring 38. Fixed to the leading edge of the hydrofoil portion 3|, as by a set screw 39, and in spaced encircling relation to the conducting ring 38, is a sleeve 48 provided with a radial opening 4I accommodating an electrically insulative support 42, as shown more specifically in Figure 5. This support carries a brush 43 slidably contactlng the ring 38 for transmitting current between conductors 44, 45 carried by the housing v3l] and the rotary cylindrical member 31, respectively. Suitable packings 46, 41, may be inserted in the sleeve 40 to seal the housing against 'waten Formed in the reduced forward end of. the cylindrical member 31, as shown in Figure 4, is a radial opening 8 containing a brush-like Contact 49 connected to the conductor 45.

Supported for rotation on the shaft 34 at its` forward end portion 35, as,4 by anti-friction bearings 50, I, is a sleeve 52 having a reduced rear end portion on which is pressed or otherwise fastened a cylindrical member 53 formed of electrically insulative material. cludes an annular flange 54 encircling the member 31 at its reduced forwardend. Embedded in the flange 54 is an electrically conductive ring 55 provided with a circular series of internally exposed contacts 56 successively ccoperable with the brush-like contact 49 upon relative movement of the cylindrical members to periodically establish electrical connection between the conductor 45 and the lwater i8 surrounding the ring 55.

The member 53 includes a reduced forward end 51 in internal screw-threaded engagement with the faired hub 58 of a screw propellerr 59 arranged to rotate at a rate depending on the rate of movement of the carriage relative t0 the Water, in the basin. At its trailing end, the hydrofoil 3| may be provided with a removable faired cap 60 enclosing the rear end of the shaft 34. Inwardly of the cap 80, a removable bushing 62 is provided to facilitate the assembly and dismantling Vof parts.

Fixed on the shaft 34, as by a set screw 63, is a sleeve 64 to which is rigidly fastened a bevel gear 65. Meshing with the gear 55 is another bevel gear 66 rigidly fixed on the lower end of a, shaft B1 which extends upwardly through the housing 30. This shaft 61 is supported for rotation, as by anti-friction bearings 68, 89. Fixed tothe upper end of the shaft 81 is a spur gear 10 meshing with another spur gear 1I. This gear 1I is fastened to the shaft 12 of an autosynchronous motor 13, electrically connected, vas by a conductor cable 14, to the generator I8 for synchronous rotation therewith. The motor 13 may be rigidly supported in a suitable chamber in the upper4 end of the housing 30, as by spaced rings 16.

In Figure 6 is shown a tachometer circuit for measuring the rate of movement of the previously-mentioned ring 55 relative to the brushlike contact 49. Serially connected to the ring 55, brush-like contact 49, conductor 45, slip ring 38, brush 43, and conductor 44, all previouslydescribed, .are a direct current source 11 and an electromagnetic relay 18, grounded at 19. The ring 55 is of course grounded by the basin water i8. In order to reduce friction between the relatively movable members 31, 53, as well as between the contacts 49, 56, a small clearance may be provided therebetween. Thus, some water may find its way into the annular space 80 shown in Figure 4. As the brush-like contact 49 passes each ring contact 56, the` water gap therebetween varies whereby an impulse is produced sufficient to energizev the' relay 18. The means for measuring the frequency of operation of the electromagnetic relay 18 may be similar to that disclosed in U. S. Patent No.` 1,611,224, granted to Nyquist. A normally closed condenser-charging circuit including a source of current 8|, resistor 82, relay contact 83, armature 84 and condenser 85 is provided. When an impulse is received by the relay, the condenser 85v is discharged through the armature 84, another relay contact 86, resistor 81 and a galvanometer 88. Since each cycle of movement of the relay armature 84 discharges a definite quantity-of electricity from the condenser 85 through the meter 88, the frequency of vibration of the relay armature will be indicated by the This member 53'inamount of current passing through the meter.

In the operation of the fluid yiiow measuring apparatus, the model 21 is towed or guided by the carriage B at any desired speed. Rotary motion of the carriage wheel I6 is transmitted to the cylindrical member 31 through the power take-off shaft 24, coupling 25, generator I8, conductor cable 14, synchronous motor 13, spur gears 1|, 10, shaft 51, bevel gears 485, 65, sleeve 64, and shaft 34. Rotary motion of the propeller 59 is transmitted to the cylindrical member 53 by the screw- `threaded connection at the propeller hub. The

propeller 59 should be designed tc make one rotation during travel through still Water over a distance substantially equal to the circumference of the carriage wheel l5. With this arrangement, the members 31, 53, will tend to rotate in synchronism during forward travel of the carriage B along the testing basin A when the water l0 therein is motionless. Under these conditions, no current will iiowin the galvanometer circuit and the galvanometer reading` will be zero. On the other hand, any Ymovement of water in the basin in the direction of travel of the carriage B caused, for instance, by movement of the model 21 through the water, will vary the propeller speed for a given carriage speed and cause relative rotation of the members 53, 31, at a rate which will be indicated by galvanometer 88.

Various changes may be made in the form of v invention herein shown and described, without departing from the spirit of the invention or the scope of the following claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.v

I claim:

l. Apparatus for use with a still-water testing basin comprising a'carriage for towing objects such as shipv models along a predetermined course through the water in such a basin, means for measuring any movement of water in the basin in the direction of ysaid course and in the vicinity ofthe towed object, said means comprising a..circuit including a source of electric current, a .switch including two relatively movable contact members, and a meter measuring thefrequencyof operation of the switch, means for imparting movement to one of said contact members at a rate depending on the rate of movement of the carriage relative to the water, and means for imparting movement to the other of said contact members at a rate depending on the rate of lmovement of the carriage relative to the basin.

2.- Apparatus for'use with a still-water testing basin comprising a carriage for towing objects such as ship models along a predeterminedcourse measuring any movement of water in the basin in the direction of said course and in the vicinity of the towed object, said means. comprising a shaft supported by the carriage for rotation about l means for measuring the rate of rotation ofthe propeller relative to the shaft.

3. Apparatus for usewith a still-water testing basin comprising a wheeled carriage for towing models along a predetermined course through the water in such a basin, means for measuring any movement of water in the basin in the direction of said course andl in the vicinity of the model being towed, said means including a shaft supported by the carriage for rotation about an axis extending in the direction of said course, a prof peller mounted `for rotation relative to the shaft, means transmitting motion from a wheel of the carriage to the shaft, and a tachometer for measuring the rate of rotation of the propeller relative to the shaft.

4. The combination with a land vehicle movable along a selected path of travel relative to a fluid, of apparatusfor measuring the ground speed of the uid in the direction of said path, includinga shaft supportedbythe vehicle for rotation about an axis extending in the direction of said path, a propeller freely rotatable on the shaft and operating in said uid,l means for rotating the shaft ,atr a rate depending on the ground speedof thelvehicle, and means for measl uring the rate of rotation of the propeller relative to the shaft.

5. The combination with a wheeled vehicle movable along a selected path of travel relative to a fluid, of apparatus for measuring the ground speed of the fluid in the direction of said path, and in the vicinity of the vehicle, comprising a shaft rotatably supported by the.v vehicle, a propeller rotatable on the shaft and operating in said fluid, means transmitting motion from a wheel of the vehicle` to the shaft, and a tachometer for measuring the rate of rotation of the propeller relative to the shaft.

6. For use with a wheeled vehicle movable along a selected path of travel relative to a uid, apparatus for measuring the ground speed of the fluid in the direction of said path, in a zone fixed with respect to the vehicle, comprising a shaft rotatably'supported by the vehicle, a propeller rotatable -on the 'shaft and operating in said fluid, means transmitting motion `from a wheel of the vehicle to the shaft including an autosynchronous motor driving the shaft and a genvpropeller in the fluid during relative flow of said fluid in a given direction with respect to said support, and means for measuring the rate of rotation of the propeller relative to the shaft comprising an electric circuit including a conductor carried by the support, a conductor carried by the shaft, a sliding connection between said conductors, and a circuit maker and breaker having two relatively movable contacts, one connected to the shaft conductor and rotatable with the shaft and the other rotatably carried by the propeller.

CHARLES A. LEE. 

